Subjective evaluation of acoustic environment in underground spaces

Previous studies have demonstrated that users' evaluation of acoustic environment such as subjective loudness or acoustic comfort depends on a series of factors in a particular space, rather than only on sound pressure levels. In this study, more than 2800 interviews have been undertaken at underground spaces in Harbin, China, to find out influencing factors to users' evaluation, considering both space conditions and demographical factors. Based on the analysis of case study results, it has been found that in underground spaces, background music is generally noticeable and preferred, and it is useful for psychologically 'masking' other less preferred sound sources. While there is a linear correlation between the measured LAeq and the subjective loudness, the relationship between the measured LAeq and the acoustic comfort evaluation is of a parabolic shape, and the acoustic comfort is the best when LAeq is around 65-70dB. There is no significant difference between different age groups, whereas people with a higher income level tend to feel that an underground space is nosier and less acoustically comfortable.